The incident occurred late last night in Dera Ismail Khan district in northwestern Pakistan's Khyber Pakhtunkhwa province bordering volatile South Waziristan tribal agency.
According to police, a mobile team of the town police station was refilling their van at Mission Morr when unidentified gunmen opened fire on them before fleeing from the scene.
Four policemen, including an Assistant Sub Inspector and two constables, were killed, police said, adding that the injured policeman was shifted to a hospital.
Police have cordoned off the area and launched a manhunt to nab the perpetrators.